Disfotopsia pseudofáquica negativa. Fenómeno visual no deseado ocasionado por lente intraocular Dilucidando el enigma. Alternativa terapéutica

The aim of this study was in the first part to determine the prevalence of negative dysphotopsia pseudophakic based on a type of intraocular lens, multifocal specifically, in a sample of 90 patients whom underwent a cataract surgery at the Centro Medico Docente La Trinidad de Caracas between the years 2004-2006 . We also evaluated the degree of satisfaction and tolerability of the negative dysphotopsia phenomenon in 70 of the 90 patients. In a second part, we evaluated 54 patients with negative dysphotopsia with different types of intraocular lenses that attend to the neuroophthalmology consultation at the Centro Medico Docente La Trinidad y la Unidad Oftalmologica de Caracas from 2006 to 2013. Prismatic lenses were used as a therapeutic alternative for negative dysphotopsia. The following variables were analyzed in both groups of patients with negative dysphotopsia: postoperative visual acuity, age, sex and laterality of the symptom. In addition, to the first group the questionnaire of the National Eye Institute Visual Functioning -25 (VFQ-25) 2000 version was applied to measure the degree of satisfaction and tolerability of this phenomenon. In the second group the prevalence of intraocular lens type was assessed. Prism lenses were employed to treat the visual phenomenon. In the first part the patients were 33 (36.7 %) male and 57 (63.3 %) female, aged between 30 and 70 years old. The prevalence of negative pseudophakic dysphotopsia was in 25.9 %; bilateral in 50 (55.6 %) and unilateral in 40 (44.4 %). Predominant visual acuity was 20/20 (0.00 logMAR) in 50 % of patients. Based in the questionnaire performed, 45 (64.3 %) patients get used to the visual phenomenom, 14 (20 %) were not and 11 (15.7 %) it disappeared. Patients showed high degree of satisfaction with the obtained visual acuity and in 54 (77 %) there was a tolerability to the phenomenon. In part two, 9 patients (17 %) were male and 45 (83 %) female, aged between 30 and 82 years old. The prevalence was higher in multifocal lenses: 30 (56 %) in relation to the monofocal 24 (44 %). No difference was found regarding the laterality (50 %). Predominant visual acuity was 20/20 in 65 % of patients. The prism slowed down dysphotopsia for far vision with 2DP value and near vision with 4 DP value. From the analysis and based on scientific evidence it was concluded that negative dysphotopsia is an undesirable visual phenomenon that arises as a result of the new intraocular lens design, that refracts the incident light in the straight edge to over 30 degree of the nasal retina causing temporarily increasing stimulation. Entoptic phenomenon explains the degree of independence of visual acuity, visual field and / or ophthalmic pathology. The prism is a therapeutic alternative in the treatment of the visual phenomenon despite the patient's large capacity of neuroadaptation.